This is a C program to find the sum of odd and even numbers from 1 to N.

The program takes the number N and finds the sum of odd and even numbers from 1 to N.

1. Take the number N upto which we have to find the sum as input.

2. Using for loop take the elements one by one from 1 to N.

3. Using if,else statements separate the element as even or odd.

4. Add the even and odd numbers separately and store it in different variables.

5. Print the sum separately and exit.

Here is source code of the C program to calculate the sum of odd & even numbers. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

`#include <stdio.h>`

void main()

`{`

int i, num, odd_sum = 0, even_sum = 0;

printf("Enter the value of num\n");

scanf("%d", &num);

for (i = 1; i <= num; i++)

`{`

if (i % 2 == 0)

even_sum = even_sum + i;

`else`

odd_sum = odd_sum + i;

`}`

printf("Sum of all odd numbers = %d\n", odd_sum);

printf("Sum of all even numbers = %d\n", even_sum);

`}`

1. User must first enter the number upto which he/she wants to find the sum and is stored in the variable num.

2. Using for loop take the elements one by one from 1 to num.

3. Use if,else statement for each element to find whether it is odd or even by dividing the element by 2.

4. Initialize the variables odd_sum and even_sum to zero.

5. If the element is even,then increment the variable even_sum with the current element.

6. If the element is odd,then increment the variable odd_sum with the current element.

7. Print the variables odd_sum and even_sum separately and exit.

Case 1: Enter the value of num 10 Sum of all odd numbers = 25 Sum of all even numbers = 30 Case 2: Enter the value of num 100 Sum of all odd numbers = 2500 Sum of all even numbers = 2550

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